1. Field of the Invention
This invention relates to a sheet feeding apparatus for feeding sheets separately one by one and an image processing apparatus using this.
2. Description of Related Art
Conventional image forming apparatus, such as laser printers, and conventional image processing apparatus, such as document scanners, have a structure in which plural sheets are set in a paper tray and separately fed one by one. Such a typical feeding apparatus is shown in FIG. 17.
Sheets S are set in a tray member 50, and a pickup roller 52 and a cam 53 coaxial with the pickup roller 52, which constitute a feeding rotary body, start rotating in a direction of arrow M upon drive of a roller shaft 51. An intermediate plate 54 is normally urged toward a direction of arrow N by a feeding spring (compression spring) 55, and a projection 54a of the intermediate plate 54 is in contact with the cam 53. The intermediate plate 54 is rotatable around a shaft 54b as a center; when the pickup roller 52 rotates in the direction of arrow M, the projection 54a of the intermediate plate 54 is disengaged from the cam 53, thereby pushing the intermediate plate 54 upward in the direction of arrow N by a feeding spring 55. This operation makes the topmost sheet of the sheet bundle in contact with the surface of the pickup roller 52 to feed the sheet in a direction of arrow P.
When sheets S are doubly fed at a time of pickup, the sheets are separated by a separation pad 56. The separation pad 56 is normally urged in a direction of arrow Q by a separation spring (compression spring) 57, thereby contacting to the pickup roller 52 always with a constant pressure. The sheet S is subsequently fed to the image processing unit 60 by way of a guide passage 59 by a feeding roller pair 58, thereby subject to a prescribed image processing.
With such a feeding apparatus thus described, however, a rotation axis (shaft 54b) of the intermediate plate 54 is located away from the pickup roller 52 to some extent, so that a position of the rotation axis determines the size of the apparatus.
To make such an apparatus compact, in a devised sheet feeding apparatus, the intermediate plate 54 is made smaller in the lengthwise direction, and the sheet pushing portion is not a rotational means but an up and down parallel moving means. However, such an apparatus moving up and down parallel the sheet pushing portion may generate impact sounds during parallel moving.
This invention is for solving the above problems. It is an object of the invention to provide a sheet feeding apparatus capable of reducing impact sounds even where a sheet pushing means operates and feeding sheets surely.
A representative structure according to the invention to accomplish the above object includes, in a sheet feeding apparatus for feeding sheets sheet by sheet separately from a placed sheet bundle, a sheet mounting portion for mounting sheets, a feeding rotary body for applying feeding force to the sheets, pushing means for pushing the sheet onto the feeding rotary body by moving in association with rotation of the feeding rotary body, and damper means for reducing impacts in connecting to a moving portion of the pushing means.
With the structure thus described, the pushing means operates with buffered impacts by the damper means even where the sheet pushing member of the pushing means is moved up and down parallel to make the apparatus compact, thereby reducing impact sounds.
The damper means may be constituted of an air damper, which operates to reduce air resistance when the pushing mean moves in a direction that the sheet is pushed toward the feeding rotary body, and thereby, the apparatus can reduce impact sound without increasing drive loads.
The sheet mounting portion or the sheet pushing member of the pushing means may be constituted having a friction coefficient of 0.1 or less with respect to a mounted sheet. A smaller frictional resistance on the sheet mount surface of the sheet mounting portion or the sheet pushing means allows sheets to be fed stably without exerting unnecessary force during sheet feeding.
A restricting portion for restricting a rear end of the mounted sheets from moving backward in a sheet conveyance direction is provided at the sheet mounting portion, thereby surely conveying the sheets.
Furthermore, an image forming means is attached to each sheet feeding apparatus described above as to form an image forming apparatus.